Type 2 diabetes has reached epidemic proportions world-wide and carries a high burden of cardiovascular morbidity and mortality. This application seeks to identify novel modifiable factors, namely plasma ceramide and sphingomyelin species, associated with risks of incident diabetes and cardiovascular disease. Ceramides and sphingomyelins are lipids (sphingolipids) that influence metabolic processes implicated in the pathophysiology of diabetes and cardiovascular diseases, including apoptosis, lipotoxicity, insulin resistance, glucose homeostasis and atherosclerosis. Until recently, all sphingolipids were thought to have similar physiological effects; however, there is now compelling evidence that sphingolipid species that carry different saturated fatty acids exhibit vastly different biological activities. We propose for the first time to examine the association of specific circulating ceramide and sphingomyelin species with incident diabetes and diabetes-related cardiovascular disease. We hypothesize that plasma ceramide and sphingomyelin species that contain the saturated fatty acid palmitic acid (16:0) are associated with higher risks of incident diabetes and diabetes-related cardiovascular disease. In contrast, we hypothesize that plasma ceramide and sphingomyelin species that contain a saturated fatty acid with 20 or more carbons (20:0, 22:0 or 24:0) are associated with lower risks of incident diabetes and cardiovascular disease. We will investigate these hypotheses in the Strong Heart Family Study, a community-based, prospective study of risk factors for cardiovascular disease among American Indians from 13 different tribes. Because of the high incidence of diabetes and early cardiovascular disease, prospectively studying the association of sphingolipid species with diabetes and cardiovascular disease among American Indians may reveal important mechanistic insights as to the pathways and processes involved. Using state-of-the-art spectrometry, we will measure 8 ceramide and sphingomyelin species in plasma from existing baseline samples from 3665 Strong Heart Family Study participants, and combine these new data with existing information on risk factors and follow- up data to examine the following specific aims: (Aim 1) To prospectively examine the associations of ceramides and sphingomyelins containing the fatty acids 16:0, 20:0, 22:0 and 24:0 with incident diabetes, and changes in fasting glucose, fasting insulin, HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) and hemoglobin A1C among participants without diabetes at baseline; and (Aim 2) To prospectively examine the associations of these sphingolipids with incident diabetes-related cardiovascular disease (including myocardial infarction, ischemic stroke, and cardiovascular mortality). The discovery of precise sphingolipid species associated with diabetes and its cardiovascular complications will point to the potentially causal pathways that need to be targeted for future interventions.